Notes on Alteration Perks

The Dual Casting perk boosts the duration of the various flesh spells but not their effect - the armor bonus conferred on the player remains the same.

Certain high end mage items (e.g., a certain mask acquired during the College of Winterhold quests) are classified as armor. Wearing them negates the bonus from the Mage Armor perk (even if the spell is cast without the item equipped).

Total Magic Resistance is capped at 85%. Depending on items one may reach this level without the Magic Resistance perk (although having the perk could free up enchantment slots for other beneficial effects).

Alteration really shines at the Expert level with the fantastic Paralyze and Ebonyflesh spells. The Expert Alteration perk is potentially a very good investment.

Dragonhide works differently than the rest of the 'flesh' line. Read the description, and keep in mind Master level spells have a long casting time, before investing in the Master Alteration perk.

Vendors

At these people you can buy Alteration spell tomes, some sell more books than others:

To get from Adept to Master in a quick fashion, you'll need two spells: Equilibrium and Telekinesis which you can get from Tolfdir in the College of Winterhold. First, cast telekinesis on a object, then cast Equilibrium fast to slower the rate at which magicka depletes (watch your health). Once you're out of magicka you can rest for an hour then repeat this process over and over till you're level 100 in Alteration. I suggest being in The Arcanaeum in the College of Winterhold because there is a lot of objects and space.